MCQ – 87351

Which type of anal fistula is seen in this image marked with red arrow?

A.	Trans-sphincteric
B.	Extrasphincteric
C.	Intersphincteric
D.	Supra-sphincteric

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Correct Answer � C Explanation

Ans.C. Intersphincteric

In the given image, the fistula traverses the internal sphincter and tracks down the space between the internal and external anal sphincters; hence, it is an inter-sphincteric type of anal fistula.

Inter- sphincteric 45%

• Arises due to Perianal abscess.
• Begins with Dentate line.
• Tracks along with Intersphincteric space.
• Ends in Perianal skin or perineum.

Trans- sphincteric 30%

• Arises due to  Ischiorectal Fossa.
• Begins from Dentate line.
• Tracks along Via internal and external sphincters to the ischio-rectal fossa.
•  Ends with Perianal skin or perineum.

Supra- sphincteric 20%

• Arises due to Supra-levator abscess.
• Begins from Dentate line.
• Tracks along Inter-sphincteric space, upwards to a point above the pubo-rectalis and downwards lateral to the external anal sphincter to the ischio-rectal fossa.
• Ends with Perineal skin or perineum.

Extra- sphincteric 5%

• Arises due to- 

1. Penetrating injury
2. Crohn’s disease
3. Carcinoma rectum

• Begins from Rectum or sigmoid colon .
• Tracks along Downward through the levator ani muscle to peri-anal skin.
• End with Peri-anal skin via ischio-rectal  fossa.